The world's fastest man, Usain Bolt, has thrown his weight into the debate over who is the best football player on the planet and claimed that it is Cristiano Ronaldo, not Lionel Messi.

Bolt, who has made it clear he would love a chance to prove his football skills in a trial with Manchester United, has shown his dominance on the athletic stage at London 2012 by successfully winning gold in the 100m, 200m and 4x100m relay for a second successive Games.

Now he insists that Barcelona star Messi, who won the Ballon d'Or in 2009, 2010 and 2011 is not quite as good as Real Madrid winger and the world's most expensive player Ronaldo.

"No doubt Cristiano is better than Messi. He is a more complete player," Bolt told Portuguese channel RTP. "I would give [the Ballon d'Or] to Cristiano. He has managed to stay on top and that's the most difficult thing."

The Jamaican's words can be taken with a pinch of salt as he is a confirmed United fan who recently claimed he would help the club in any way to "make sure the title does not end up with Manchester City again".

One thing he has noticed in the United line-up is a weakness in the sprinting department: "You see guys like Nani and Ashley Young who are so fast and skilful, but they get pushed off the ball like Ronaldo used to," he explained.

"Since I taught Ronaldo in 2009 he has gone on to score 40 goals a season, I don't think he would have scored them all without my training. United have so many players with pace that if they all perfect their sprinting technique it will be impossible to play against them."